Our ancestors lived on shaky ground

Our earliest ancestors
preferred to settle in locations that have something in common with cities such
as San Francisco, Naples and Istanbul – they are often on active tectonic
faults in areas that have an earthquake risk or volcanoes, or both.

Regions vulnerable to earthquake
and volcanic activity often create landscapes with long-term benefits for human
settlement

Professor Geoff Bailey

An international team of
scientists has established a link between the shape of the landscape and the
habitats preferred by our earliest ancestors. The research, by scientists at the University of the Witwatersrand,
South Africa, the University of York and the Institut de Physique du Globe
Paris (IPGP), is published in the March 2011 issue of the Journal of Human Evolution.

The four-year study examines
the geomorphology (literally the shape of the landscape) around ancient sites
in southern Africa.

Lead author, South African
Dr Sally Reynolds, a palaeoanthropologist at Witwatersrand who conducted the
research during a postdoctoral fellowship at IPGP, says: “We were stunned when during a fieldwork trip
in South Africa in 2007, Professor Geoffrey King and I discovered evidence that
hominin sites such as Taung, Sterkfontein and Makapansgat, show landscape
features in combinations that are not random, but result from tectonic motions,
such as earthquakes.”

Several lines of scientific
evidence suggest that Australopithecus
africanus (like the ‘Mrs Ples’ fossil from Sterkfontein) was adapted to
mixed, or mosaic habitats – landscapes with trees and open grassland, with
some wetland marshy areas. The study
suggests that it was the type of mosaic environment created by tectonic earth
movements near rivers or lakes.

These features including
cliffs, sedimented valleys, river gorges and drier plateau areas in close
proximity of about 10 kilometres, are created when sections of the earth’s
crust move in response to pressure, then blocks of land are lifted up, while
others are forced downwards. When this
happens next to a river, the result is the creation of wetland, marshy areas
close to drier plateaus and areas of erosion.

Professor Geoff Bailey, from
the University of York, who is the lead author on an accompanying paper, also
published in the same issue of the Journal
of Human Evolution, confirms: “This link between earthquakes and human
habitation is one we’ve long suspected was there. Regions vulnerable to earthquake
and volcanic activity often create landscapes with long-term benefits for human
settlement. But the tragic events in Christchurch are a graphic illustration of
the attendant risk of these locations.”

Professor King, a tectonic
geomorphologist at the IPGP, adds: “The
original idea was developed in Greece over a decade ago, with the surprising
discovery that the sites there were clearly associated with ongoing tectonic
activity.

“Even though South Africa appears to be
tectonically stable, there are landscape features that indicate that modest
levels of activity are preserved in the hard, southern African rocks. This
means that the landscape model we developed in Greece is equally applicable to
East Africa, and now also to the well-known fossil sites of the South Africa’s
Cradle of Humankind World Heritage Site.”

Dr Reynolds, who is also an
honorary research fellow at the School of Natural Sciences and Psychology at
Liverpool John Moores University, explains “Our hominin ancestors would have
been unaware of the tectonic influence on their habitats, but instead would
have been attracted by the range of food and shelter offered.”

The combination of drinking
water, steep cliffs that provided shelter from predators, together with a range
of feeding sources constitute the key ingredients for an ideal habitat for our
ancestors.

Dr Sally Reynolds is an honorary research staff member of the Institute for Human Evolution, University of the Witwatersrand, South Africa and Liverpool John Moores University, UK. She conducts research on the world-famous Sterkfontein Cave fossils from the Cradle of Humankind World Heritage Site and is interested in the role of landscape use and extinction in hominins. Dr Sally Reynolds is available for interviews on +33 6 58627039 (mobile).

Professor Geoff Bailey is an Anniversary Professor of Prehistoric Archaeology in the Department of Archaeology at the University of York and is engaged in field research on the early prehistory and submerged landscapes of the southern Red Sea region in Saudi Arabia. More information at: www.york.ac.uk/archaeology/staff/academic-staff/geoff-bailey/

Professor Geoffrey C. P. King is a Professor in Tectonic Geomorphology at the Institut de Physique Du Globe, Paris, and an Honorary Visiting Professor at the University of York. He conducts research on earthquakes mechanisms, mountain building and the evolution of human landscapes. More information at www.ipgp.fr/~king/Geoffrey_King/Home.html